基于水化反应动力学的深水固井井筒温度与压力耦合预测模型

A coupled model of temperature and pressure based on hydration kinetics during well cementing in deep water

针对深水固井候凝期间水泥浆温度、压力与水化反应之间复杂的相互作用,基于水泥浆水化反应动力学建立深水固井候凝井筒温度压力耦合模型,利用差分法进行耦合数值求解,并将计算结果与实验及现场数据进行对比以验证模型的准确性。考虑水化反应、温度、压力之间的相互作用时,新建立的固井井筒温度压力耦合模型计算精度在5.6%以内,能够很好地满足工程要求。结合深水井开展数值模拟分析候凝期间井筒温度、压力、水化度的演化规律,研究结果表明:水泥浆温度在水化热作用下会迅速升高;随着水泥浆胶凝强度的发展,水泥浆的孔隙压力会逐渐降低,甚至低于地层压力,从而引发气窜;瞬态变化的温度和压力会影响水泥浆水化反应速率,井筒深部的水泥浆在高温高压环境下具有更快的水化反应速率;对于深水固井作业来说,泥线附近的低温环境会延长水泥浆的候凝时间,导致固井工作周期变长。

Considering the complicated interactions between temperature,pressure and hydration reaction of cement,a coupled model of temperature and pressure based on hydration kinetics during deep-water well cementing was established.The differential method was used to do the coupled numerical calculation,and the calculation results were compared with experimental and field data to verify the accuracy of the model.When the interactions between temperature,pressure and hydration reaction are considered,the calculation accuracy of the model proposed is within 5.6%,which can meet the engineering requirements.A series of numerical simulation was conducted to find out the variation pattern of temperature,pressure and hydration degree during the cement curing.The research results show that cement temperature increases dramatically as a result of the heat of cement hydration.With the development of cement gel strength,the pore pressure of cement slurry decreases gradually to even lower than the formation pressure,causing gas channeling;the transient temperature and pressure have an impact on the rate of cement hydration reaction,so cement slurry in the deeper part of wellbore has a higher rate of hydration rate as a result of the high temperature and pressure.For well cementing in deep water regions,the low temperature around seabed would slow the rate of cement hydration and thus prolong the cementing cycle.